textproduct: Rapid City

KEY MESSAGES

- Mild and windy conditions for most of the upcoming week.

- Mainly dry, a few sprinkles/flurries possible this afternoon/evening.

- Near record high temperatures Monday and Wednesday.

DISCUSSION

(Today Through Saturday) Issued at 203 AM MST Sun Dec 21 2025

Latest upper level analysis shows quasi-zonal flow over the forecast area with weak ridging building over the western CONUS and a deepening low over the Gulf of Alaska/Pacific Ocean. At the surface, high pressure is in place with a stationary boundary extending through eastern Montana and central South Dakota. Temperatures at 08Z are mainly in the 20s.

The upper ridge shifts slowly east today and tonight as the Pacific upper low deepens. Warm air advection ahead of the next impulse will support highs in the low 40s to low 50s. Mid and high level moisture increases, resulting in increased cloud cover across the forecast area. Weak frontogenesis may result in a few sprinkles and flurries this afternoon and evening.

Southwesterly winds will increase tonight across northeast WY, the Black Hills, and eastern foothills with increased flow aloft and a tightening pressure gradient. This could support advisory level winds in the foothills after midnight tonight and during the day on Monday when the strongest pressure gradient will be in place across the Hills. Downslope winds and prefrontal conditions will result in warm temperatures on Monday which will approach near record highs as most records are in the mid-60s.

A dry cold front moves through the area late Monday/Monday evening, switching the winds around to the northwest and bringing in a little bit of colder air. Warm air advection quickly begins early Tuesday, allowing highs over the southwestern portion of the forecast area to be similar to Monday. However, highs on the South Dakota Plains will be 5F to 10F cooler on Tuesday.

Conditions Tuesday night and Wednesday will be similar to tonight and Monday, as increasing warm air advection, westerly flow, and downslope winds will allow for near record highs on Christmas Eve.

Model consistency lessens beginning on Christmas, due to the timing of the next cold front/upper trough as the strong upper low off British Columbia weakens and dives southward down the California Coast. The timing and strength of the next cold front/upper trough ejecting over the Rockies will greatly influence conditions on Christmas. Most deterministic models and the the mean ensembles delay the arrival, allowing for warmer conditions to continue. As this system moves across the forecast area, there could be a chance of light precipitation due to cold air over running the warm air.

AVIATION

(For the 18Z TAFS Through 18Z Monday) Issued At 1041 AM MST Sun Dec 21 2025

VFR conditions are expected through the TAF period. Southwest winds will increase early this evening across portions of northeastern Wyoming and the Black Hills. There will be a short period of low level wind shear (around 30 knots) across northeast Wyoming and the Black Hills from 22Z to 03Z before the winds increase at the surface.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.